The known process for preparing ethambutol-isoniazid-methane sulfonates is disclosed in No. 2036935 in the German Patent Gazette for Public Inspection. In the prior art isoniazid-methane sulfonic acid or its sodium salt is produced through reaction in water, and separated and purified and then this reacted with ethambutol in alcoholic solvents such as methanol or ethanol, to produce ethambutol-isoniazid-methane sulfonate.
However, in this process, if isoniazid-methane-sulfonic acid or its sodium salt is reacted with ethambutol without any separation, this method results in a low yield of the final products e.g. 60% and high cost.
Furthermore, it is time-consuming to separate or crystallize the ethambutol-isoniazid-methane sulfonate.
Moreover, in the prior art technique as set forth above, it is impossible to obtain an ethambutol-isoniazid-methane sulfonates having a satisfactorily high activity.
In order to overcome these disadvantages, present the invention relates to an improved process for preparing ethambutol-isoniazid-methane sulfonate.